1. Field of the Invention
The present invention relates to devices and techniques for controlling and initiating the explosion of explosives.
2. Background Art
Ever since explosives were first invented, attempts have been made to control and initiate their explosion. Since explosives can be harmful to anything in the vicinity of their explosion, fuzes have been developed to prevent explosion near those using the explosives and to cause explosion at the intended location of the explosion. Mechanical, chemical and electrical fuzes have been developed, as well as those relying on other physical principles and phenomena. Fuzes have been designed to provide sensitivity to elapsed time, proximity to a target, impact, and other factors. Fuzes often include a safety features to prevent inadvertent explosions. Some examples of attempts to control and initiate explosions are described below.
U.S. Pat. No. 3,739,726, issued to Pintell, discloses a fuze for ordnance projectiles to be launched from a vehicle, wherein the fuze is armed after separation from its launcher by mechanical closure of switches with the aid of a delayed-action squib detonating by an electric charge stored on a capacitor. The fuze system includes means for charging the above capacitor at the instant in time at which the projectile is launched. Pintell requires the capacitor to be charged with high current levels and does not allow charging to occur at lower current levels prior to the instant in time at which the projectile is launched. Furthermore, Pintell does not provide a means for discharging the capacitor once it has been charged so as to reset the fuze to an inert state.
U.S. Pat. No. 4,445,435, issued to Oswald, discloses an electronic delay blasting circuit comprising digital counting circuitry. A two-wire input is provided to a bridge rectifier. When power is applied across the two-wire input, the bridge rectifier provides rectified power to charge a capacitor. When the capacitor is sufficiently charged, the digital counter circuit is initialized. As long as power is applied across the two-wire input, the counter circuit does not count. When power is removed from the two-wire input, the counter circuit counts for number of counts that has been set in advance with a binary switches. When the counting process is completed, a silicon controlled rectifier (SCR) is triggered, discharging the capacitor into an electric match for igniting an explosive charge. Oswald does not teach a digital counter circuit capable of being programmed remotely. Oswald also does not teach a method of restoring the circuit to an inert state after the capacitor has been charged. Rather, Oswald teaches a blasting circuit where actuation of the electric match appears to be inevitable after the capacitor has been charged.
U.S. Pat. No. 4,825,765, issued to Ochi et al., discloses a delay type electric detonating primer including a capacitor for storing electric charge and a clock pulse generating circuit having a crystal oscillator. A power source is supplied to a two-terminal input of the primer. Power from the power source is used to charge the capacitor. When power is removed from the two-terminal input, an actuation signal is produced that causes a counting circuit to start counting clock pulses from the clock pulse generating circuit. When the counting circuit counts to a value that has been set using binary switches, an ignition signal is generated. A switching circuit that includes an SCR then applies the charge in the capacitor to an igniting resistor, which ignites an explosive charge. Ochi et al. do not teach a digital counter circuit capable of being programmed remotely. Ochi et al. also do not teach a method of restoring the circuit to an inert state after the capacitor has been charged. Rather, Ochi et al. teach a blasting circuit where actuation of the electric match appears to be inevitable after the capacitor has been charged. Furthermore, Ochi et al. require an expensive crystal oscillator, which may be damaged or adversely and unpredictably affected by high acceleration. Thus, the blasting circuit of Ochi et al. is unsuitable for incorporation into projectiles.
U.S. Pat. No. 4,712,477, issued to Aikou et al., discloses an electronic delay detonator for igniting an ignition resistor. DC power from a blasting machine is connected to a two-wire input of the detonator. The DC power passes through a bridge rectifier and charges a power supply capacitor and the capacitor of an RC circuit. The RC circuit is connected to a comparator and provides a time delay after DC power is applied to the two-wire input of the detonator. After the time delay, the comparator changes state, causing a latch circuit to trigger a current switching circuit to apply current from the power supply capacitor to a detonator ignition resistor. The detonation ignition resistor ignites an explosive charge. Aikou et al. do not teach a fuze incorporating a digital timing circuit. Aikou et al. also do not teach a fuze where a capacitor can be charged before the time delay period begins. Furthermore, Aikou et al. do not teach a fuze that may be restored to an inert state after the power supply capacitor has been charged. Additionally, Aikou et al. do not teach a fuze where the timing period may be remotely programmed.
U.S. Pat. No. 4,233,673, issued to Cricchi et al., discloses an electrically resettable non-volatile memory for a fuse system. The memory has a plurality of storage bits, each bit comprising a insulated gate field effect transistor (IGFET). The IGFETs may be set one of two threshold voltage states to represent binary information. The binary information may be read back from the IGFETs. A fire command transfers the binary information to a counter. The counter is then operated at a predetermined clock rate until overflow occurs for generating a signal for detonating the explosive projectile. Cricchi et al. do not teach a fuze system where the projectile is coupled to the launcher by a 2-wire non-polarized connection, but rather Cricchi et al. teach a terminal box requiring four terminals, the orientation of which is inflexible. Furthermore, Cricchi et al. do not teach a method for providing frequency compensation for an oscillator in the projectile.
U.S. Pat. No. 4,424,745, issued to Magorian et al., discloses a digital timer fuze. When a pilot arms the system and selects a firing mode, power is supplied to each fuze in the load. When the firing button (pickle switch) is depressed, timing commands are injected into each fuze and the rocket motors are initiated. As each rocket moves forward under motor thrust, the lead to its fuze is separated. Physical interruption of this circuit initiates the "run" phase of the digital timer fuze. The digital time fuze is electrically connected to a fuze setter. A signal from the fuze setter charges a power supply capacitor and causes a counter to count clock pulses for a given period of time and store the count. When the umbilical line connecting the fuze to the fuze setter is severed, the main counter counts down at a given rate. When all of the stored counts have left the counter, the counter gates an SCR which allows the power supply capacitor to actuate the detonator. Magorian et al. do not teach a method for compensating the frequency of an oscillator in a projectile. Magorian et al. do not teach the initiation of a final counting sequence prior to launch or the confirmation of launch after some time period subsequent to the launch. Furthermore, Magorian et al. requires an discrete SCR firing circuit. Magorian et al. does not teach a firing circuit that can be formed in an integrated circuit (IC) along with oscillator and counter circuitry.
U.S. Pat. No. 4,421,030, issued to DeKoker, discloses an electronic safe and arm device for generating a trigger signal for initiating detonation of a flying plate detonator. A normally closed arm enable switch prevents the charging of the trigger capacitor until after break-wire launch has occurred. DeKoker does not teach the charging of a capacitor prior to launch. DeKoker detonates an explosive upon impact with a target. DeKoker does not teach the use of timer to ignite an explosive charge after a preset time.
U.S. Pat. No. 3,500,746, issued to Ambrosini, discloses an electronic time fuze mounted in a projectile is connected to ground equipment through an umbilical cord until the projectile is launched. The umbilical cord exchanges information between the fuze and the ground equipment so the fuze can more accurately measure the time elapsed from projectile launch to detonation. The fuze includes a local oscillator that is energized by the power stored in the capacitor. Output pulses from the local oscillator are coupled through a launch gate to a counter which is set prior to launch. After the projectile is launched, the local oscillator pulses count down the setting of the counter until a zero state is reached, at which time the detonator is actuated. Prior to launch, the counter is set, errors in the frequency of the local oscillator are compensated for, and the power supply capacitor is charged through the umbilical cord. The errors in the local oscillator frequency are compensated for either by modifying the initial setting of the Counter or correcting the frequency itself of the local oscillator. Ambrosini does not teach ignoring any signals present at the connecting wires of the projectile for a period of time at launch. Ambrosini does not teach the use of a two-wire non-polarized connection for providing power to the fuze and for transmitting signals to and receiving signals from the fuze.
U.S. Pat. No. 3,964,395, issued to Kaiser et al., discloses an electrical primer for projectiles in which the charge on a capacitor is stepwise reduced by periodic timing pulses to a level at which the projectile is armed. Kaiser et al. do not teach a method for setting a digital counter remotely. Kaiser et al. do not teach a method for remotely compensating for frequency inaccuracies of an RC oscillator in a projectile.
Furthermore, the above references are directed toward military ordnance. The present invention is useful for fireworks and pyrotechnic displays. It is generally not economical to apply devices intended for use in military ordnance to fireworks and pyrotechnic displays because such devices are generally complicated and expensive. Prior art devices providing communication to the fuze have required multiwire connections, typically involving four or more wires, where the order of the wires had to be maintained. Mismatching of the wires in prior art devices leads to failures, misfires and/or safety hazards. Also, such devices may be made of materials that could be harmful to spectators and others and to the environment. Moreover, there is nothing to suggest the combination of the above references or their application, either alone or in combination, to fireworks and pyrotechnic displays. Thus, a simple, inexpensive, safe and reliable time fuze applicable to fireworks and pyrotechnic displays is needed.
U.S. Pat. No. 3,068,756, issued to Schermuly, discloses a discharger for pyrotechnic devices that uses a conventional electrical igniter to ignite an explosive charge to eject a container from a casing. Schermuly does not disclose an electronic fuze to be ignited after a time delay after launch. Schermuly also does not teach the use of a digital timing circuit. Furthermore, Schermuly does not teach the use of an electrical energy storage means in the projectile.
Traditionally, fireworks have been simply constructed. A typical fireworks shell includes an initial fuze, an initial charge, a main fuze and a main charge. These fuzes and charges are chemical based. The initial fuze is ignited by a technician and allow the technician time to get away from the shell before the initial charge explodes. The initial fuze ignites the initial charge. The initial charge ignites the main fuze and propels the main charge into the sky. The main fuze provides a delay which allows the main charge to reach the desired burst location. After the delay, the main fuze ignites the main charge.
Prior art fireworks have not been as safe or reliable as desired. Once the initial fuze is ignited, the initial charge, the main fuze and the main charge are ignited in sequence with no way to interrupt the process. Also, chemical time delay fuzes have been somewhat inaccurate and unpredictable. Furthermore, it has not been possible to easily and quickly test the components of an assembled shell in an automated manner prior to launch.